Not sure what size Grain Bunker Size you need for your desired capacity? Try our Grain Bunker Calculator.
Not sure what size Grain Bunker Size you need for your desired capacity? Try our Grain Bunker Calculator.
Harvest has a way of arriving faster than expected, and a grain bunker that isn’t ready when the first truck rolls in can turn a smooth harvest into a scramble. Whether you’re running an existing bunker for another season or setting one up for the first time, a bit of preparation now saves you from moisture damage, spoilage and lost tonnage later.
This checklist splits into two parts: what to check if you already have a bunker in place, and what to plan for if you’re building one from scratch this season.
If you’ve used your bunker before, the good news is most of the hard work is already done. But tarps and pads take a beating over a full storage cycle, and a few minutes of inspection now can prevent a much bigger problem once grain is loaded.
Your top tarp and ground sheet have likely spent months exposed to UV, wind and temperature swings since they were last used. Fabric that looked fine at pack-away can develop weak points over the off-season. Before harvest:
As a general guide, a well-cared top tarp should last around three years and a ground sheet closer to one to two years, so factor the age of your covers into how closely you inspect them this season.
A pad that’s rutted, pooling water or has lost its camber will undermine even a brand-new tarp. Before filling:
A pad in good condition protects everything you put on top of it, so it’s worth the extra half hour before the season gets underway.
If you’re building a bunker for the first time this season, there’s more to plan, but getting the fundamentals right from the start avoids a much more costly fix down the track.
Before you break ground, it’s worth watching our grain bunker construction and operation video, which walks you through the entire process from site selection to sealing and outloading. It’s a practical resource that covers the process visually, and it’s worth revisiting once you’ve read this checklist so the two reinforce each other.
Your pad is the foundation everything else depends on. At a minimum, it needs to sit above ground level and any flood-prone areas, with all-weather access on both sides for trucks and machinery. A slight camber, with a small rise in the centre, helps subsoil moisture drain to the sides rather than sitting under your grain. Round ends generally work better than square corners too, since square ends leave depressions where water can pool unless grain is deliberately pushed into them.
The right choice depends on your site and budget as much as anything else. No walls is the fastest, most cost-efficient option and works well combined with the sealing method covered in our guide to sealing a grain bunker. Earth walls are a proven, long-standing option that use soil from the surrounding area. Concrete walls increase capacity on the same footprint and make sealing easier with clamps and rails. Steel walls are a cheaper alternative to concrete but come with their own hygiene challenges from condensation. And poly bunker walls offer a self-supporting, no-earthworks setup that can be established with just one or two people, a strong alternative to grain bags where you need flexibility.
Auger size and bunker width are directly linked, and getting this wrong before you build means reworking your pad later. As a rough guide, a 15m wide bunker needs at least a 60ft auger, a 20m bunker needs a 70ft auger, 25m needs 85ft, and 30m needs a 100ft auger for common grains like wheat, barley, sorghum, and chickpeas. Confirm your auger’s reach against your intended bunker width before you finalise the pad dimensions.
Undersized tarps are one of the most common and most avoidable mistakes new bunker owners make. Tarp size depends on your bunker’s width, length, wall height and the angle of repose of the grain you’re storing, all of which vary between grain types. Rather than estimating, run your dimensions through the Grain Bunker Calculator to get an accurate tarp and ground sheet size, along with an estimate of total volume and weight, before you place your order.
Harvest timing is unpredictable enough without your storage becoming the bottleneck. A few weeks before harvest, run through this checklist – patch any tarps, firm up the pad and finalise your wall choice and auger match. That way your bunker is ready the moment grain starts moving, not scrambled together on the day.
Aim to start at least a few weeks out. This gives you enough time to patch or replace tarps, repair the pad or in the case of a new bunker, complete earthworks and confirm equipment before grain needs to go in.
Skipping a full tarp inspection and only checking the areas that were visible when it was packed away. Small holes near folds and seams are easy to miss and are exactly where problems tend to start.
A well-maintained top tarp typically lasts around three years, so reusing it is usually fine as long as it passes a thorough inspection. Ground sheets wear faster, generally lasting one to two years, so check these more closely.
Auger reach needs to match your intended bunker width. As a starting point, a 15m wide bunker needs roughly a 60ft auger, scaling up to a 100ft auger for a 30m wide bunker, though it’s worth confirming against your specific auger and grain type.
Finalising pad dimensions before confirming auger reach and tarp sizing. These three decisions are interdependent, so it pays to plan them together rather than locking in the pad first and working backwards.
Whether you’re refreshing an existing bunker or building your first one from the ground up, getting the details right now protects your grain and your bottom line later. Polytex has over 50 years of experience helping Australian growers and bulk handlers plan, build and maintain grain bunkers that perform season after season.
Call 1300 059 003 or email [email protected] to talk through your setup and explore our full range of grain bunker packages for everything you need to get storage-ready before this year’s harvest.